The next wave of high end consumer SSDs will begin shipping this month, and I believe Corsair may be the first out the gate. Micron will follow shortly with its C400 and then we’ll likely see a third generation offering from Intel before eventually getting final hardware based on SandForce’s SF-2000 controllers in May.
This just in from Consumer Electronics Show in Las Vegas, via Anandtech. SandForce SF-2000 scheduled to drop in May of this year. Get ready as you will see a huge upsurge in releases of new SSD products attempting to best one another in the sustained Read/Write category. And I’m not talking just SSDs but PCIe based cards with SSD RAIDs embedded on them communicating through a 2 Lane 8X PCI Express interface. I’m going to take a wild guess and say you will see products fitting this description easily hitting 700 to 900 MB/s sustained Read and Write. Prices will be on the top end of the scale as even the current shipping products all fall in to the $1200 to $1500 range. Expect the top end to be LSI based products for $15,000 or third party OEM manufacturers who might be willing to sell a fully configured 1TByte card for maybe ~$2,000. After the SF-2000 is released, I don’t know how long it will take for designers to prototype and release to manufacturing any new designs incorporating this top of the line SSD flash memory controller. It’s possible as the top end continues to increase in performance current shipping product might start to fall in price to clear out the older, lower performance designs.
This is a really good technical article on attempts made by Micron and Intel to fix read/write errors in their Solid State memory based on Flash memory chips. Each revision of their design and materials for manufacture helps decrease the size of the individual memory cells on the flash memory chip however as the design rules (the distance between the wires) decrease, random errors increase. And the materials themselves suffer from fatigue with each read and write cycle. The fatigue is due in no small part (pun intended) on the size, specifically thickness of some layers in the sandwich that make up a flash memory cell. Thinner materials just wear out quicker. Typically this wearing out was addressed by adding extra unused memory cells that could act as a spare memory cell whenever one of them finally gave up the ghost, stopped working altogether. Another technique is to spread reads/writes over an area much greater than (sometimes 23% bigger) than the size of the storage on the outside of the packing. This is called wear levelling and it’s like rotating your tires to ensure they don’t start to get bare patches on them too quickly.
All these techniques will only go so far as the sizes and thickness continue to shrink. So taking a chapter out of the bad old days of computing, we are back into Error Correcting Codes or ECC. When memory errors were common and you needed to guarantee your electronic logic was not creating spontaneous errors, bits of data called parity bits would be woven into all the operations to insure something didn’t accidentally flip from being a 1 to a 0. ECC memory is still widely used in data center computers that need to guarantee the spontaneous bits don’t get flipped by say, a stray cosmic ray raining down upon us. Now however ECC is becoming the next tool after spare memory cells and wear leveling to insure flash memory can continue to grow smaller and still be reliable.
Two methods in operation today are to build the ECC memory controllers into the Flash memory modules themselves. This raises the cost of the chip, but lowers the cost to the manufacturer of a Solid State Disk or MP3 player. They don’t have to add the error correction after the fact or buy another part and integrate it into their design. The other more ‘state of the art’ method is to build the error correction into the Flash memory controller (as opposed to the memory cells), providing much more leeway in how it can be implemented, updated over time. As it turns out the premier manufacturer/designer of Flash memory controllers SandForce already does this with the current shipping version of their SF-1200 Flash memory controller. SandForce still has two more advanced controllers yet to hit the market, so they are only going to become stronger if they have already adopted ECC into their current shipping product.
Which way the market chooses to go will depend on how low the target price is for the final shipping product. Low margin, high volume goods will most likely go with no error correction and take their chances. Other higher end goods may adopted the embedded ECC from Micron and Intel. Top of the line data center purchasers will not stray far from the cream of the crop, high margin SandForce controllers as they are still providing great performance/value even in their early generation products.
What OCZ (and other companies) ultimately need to do is introduce a SSD controller with a native PCI Express interface (or something else other than SATA). SandForce’s recent SF-2000 announcement showed us that SATA is an interface that simply can’t keep up with SSD controller evolution. At peak read/write speed of 500MB/s, even 6Gbps SATA is barely enough. It took us years to get to 6Gbps SATA, yet in about one year SandForce will have gone from maxing out 3Gbps SATA on sequential reads to nearing the limits of 6Gbps SATA.
It doesn’t appear the RevoDrive X2 is all that much better than four equivalent sized SSD drives in a four drive RAID Level 0 array. But hope springs eternal, and the author sums up where manufacturers should go with their future product announcements. I think everyone agrees SATA is the last thing we need to get full speed out of the Flash based SSDs, we need SandForce controllers with native PCIe interfaces and then maybe we will get our full money’s worth out of the SSDs we will buy in the near future. As an enterprise data center architect, I would seriously be following these product announcements and architecture requirements. Shrewdly choosing your data center storage architecture (what mix of spinning disks and SSD do you really need) will be a competitive advantage for data mining, Online Transaction Processing, and Cloud based software applications.
Until this article came out yesterday I was unaware that OCZ had an SSD product with a SAS (Serial Attached SCSI) interface. That drive is called the IBIS and OCZ describes the connector as HSDL (High Speed Data Link-an OCZ created term). Benchmarks of that device have shown it to be faster than it’s RevoDrive counterpart which uses an old style native hard drive interface (SATA). Anandtech is lobbying to dump SATA altogether even now that the most recent SATA version supports higher throughput (so called SATA 6). The legacy support built into the SATA interface is absolutely unnecessary given the speed of today’s flash memory chips and the SSDs they are designed into. SandForce has further complicated the issue by showing that their drive controllers can vastly out pace even SATA 6 drive interfaces. So as I have concluded in previous blog entries PCIe is the next logical and highest speed option after you look at all the spinning hard drive interfaces currently on the market. The next thing that needs to be addressed is the cost of designing and building these PCIe based SSD drives in the coming year. $1200 seems to be the going price for anything in the 512GB range with roughly 700MB/second data throughput. Once the price goes below the $1,0000 mark, I think the number of buyers will go up (albeit still niche consumers like PC Gamers). In the end we can only benefit by manufacturers dumping SATA for the PCIe interface and the Anandtech quote at the top of the blog, really reinforces what I’ve been observing so far this year.
SandForce has now announced an SF-2000 controller that doubles up the I/O performance of the SF-1500. The new product runs at 60,000 sustained read and write IOPS and does 500MB/sec when handling read or write data. It uses a 6Gbit/s SATA interface and SandForce says it can make use of single-level cell flash, MLC or the enterprise MLC put out by Micron.
Sandforce is continuing to make great strides in its SSDdisk controller architecture. There’s no stopping the train now. But as always read the fine print on any SSD product you buy and find out who manufactures the drive controller and what version it is. Benchmarks are always a good thing to consult too before you buy.